Electric resistance rod annealing furnace



2 Sfieets-Sheet 1 G M. LITTLE ELECTRIC RESISTANCE ROD ANNEALING FURNACE Filed March 23, 1922 May 27 1924.

WITNESSES: WW 1 277 6" 9 mm 3 Q m ww & mm mm B May 27, 1924. Y 1,495,856

G. M. LITTLE ELECTRIC RESISTANCE ROD ANNE/ LING FURNACE Fig 3 I garge l1. Liffle I E A'i'TORNEY 4 Patented May 27, 1924.

UNITED STATES PATENT OFFICE.

GEORGE M. LITTLE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC RESISTANCE ROD ANNEALING FURNACE.

Application filed March 23, 1922. Serial No. 546,018.

To all whom it may concern:

Be it known that I, GEORGE M. LITTLE, a citizenof the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement .in Electric Resistance Rod Annealing Furnaces, of which the following is a specification.

My invention relates to electric furnaces and particularly to electric-resistance furnaces and it has for one of its objects to provide a relatively simple and compact multiple-chamber furnace for heat treating refractory resistance rods. ,7

Another object of my invention is to provide an elongated refractory heating element for a furnace of the above indicated character that shall be composed of a plurality of units and that shall be located in, and supported by, granular heat-insulating material.

Another object of my invention is to provide a multiple-chamber refractory-rod annealing furnace with an enclosing casing that shall be provided with means for resiliently compressing the refractory electrodes and the heating element to maintain them in close operative engagement .with each other.

Another object of my, invention is to provide a furnace structure of the above indicated character that shall have a temperature in the annealing chambers which increases uniformly from the ends to the middle of the furnace.

Another object of my invention is to provide means for slowly pushing a plurality of rods in end-to-end abutting relation through the chambers, which means shall have a quick return motion.

In practising my invention, L provide a plurality of relatively thin refractory plates, each having a plurality of spaced-apart openings therethrou h, which plates are so placed as to bring the at faces in operative engagement with each other. An elongated, solid refractory electrode is located at each end of the heating element in operative engagement therewith, a plurality of openings extending longitudinally through each electrode and registering with the openings in the plates of the heating element. A water-cooled metallic electric-circuit-terminal is clamped on each of the electrodes at the outer end thereof. An elongated metallic casing havin one end wall movable longitudinally, relatlvely to the casing, surrounds the heating element and the electrodes, and resilient means is provided to press the movable end wall towards the casing and thereby also ress the refractory plates against each ot er and the refractory electrode against the built-up set of plates. A mass of finely divided granular heat-insulating material is located in the casing surrounding the heating element and the greater part of the length of the electrodes, and partly supports the heating element. A motor-operated means is provided for pushing the rods to be heat treated slowly through the chambers, provision being made for a quick return of the mechanism to its starting position.

In the drawings,

Figure 1 is a top plan view of an lectric furnace embodying my invention;

Fig. 2 is a view, partly in side elevation and partly in vertical longitudinal section, of a furnace embodying my invention;

Fig. 8 is a view, in side elevation, of an electric furnace with a rodpushing means embodying my invention;

Fig. 4 is a view, in vertical lateral crosssection, of I an electric furnace embod ing my invention, taken on the line IVI of Fig. 2;

Fig- 5 is a top plan view of the rod-pushing means and one end of an electric furnace embodying my invention;

Fig. 6 is a schematic representation of the train of gear wheels employed in the rodpushing means.

An electric-resistance furnace, designated generally by the numeral 11, comprises an elongated open-top metal casing 12 which may be substantially rectangular or square in lateral cross-section and which may be composed of a number of plates of relatively thin sheet metal in any desired manner. The casing 12 is rovided, at one end, with a metallic endate 13 and a second inner end plate 14 of a suitable insulatin material, such as asbestos lumber. A plurality of members 15, of substantially channel section,

are suitably secured against the bottom, top and sides of the furnace casing in order to 'provide stiffening ribs for the relatively thin sheet material, and the members 15 located at the sides of the casing may be provided with integral extensions 16 to constitute supporting members for the furnace structure. A plurality of doors 17 may be employed to cover the open-top casing 12, thesedoors being secured to the casing by means of hmge members 18 of any suitable or desired construction. Each of the doors may further be provided with handles 19 to permlt of raising the doors whenever desired. As illus trated in Fig. 1 of the drawings, the doors are subs tantially one-half the length of the furnace, and. two doors are employed to cover each half of the furnace casing.

'An end wall member 21 is provided at one end of the furnace casing and comprises a plurality of stiffening members 15 and integral supports 16 together with a relatively short casing 22, which is of such dimensions as to fit within the casing 12, and the member 21 is movable longitudinally of the furnace structure to permit of employing compressing means to be hereinafter described in detail. The end wall member 21 also comprises a metal end plate 23 suitably secured against the casing 22 and the stiffening members 15.

A heating element 24 is located within the casing 12 in substantially the middle portion thereof and com rises a plurality of relatively thin, fiat, re ractory, carbonaceous plates 25, which are located in-face-to-face abutting relation, each plate having a plurality of openings 25" therethrough. At each end of the heating element 24 is located an elongated, solid, cylindrical. refractory. carbonaceous electrode 26 which extends to within substantially a short distance of the inner surface of the plate 13 and of the plate 23 at the two ends of the furnace and is provided with a plurality of longitudinally extending chambers 26 therethrough "which register with the openings 25 to constitute passageways for the material being heat treated. The plates 25 may each comprise a single plate substantially square in contour or may comprise a plurality of smaller plates, as may be found necessary or desirable. The diameter of each of the electrodes 26 is substantially equal to the length of the diagonal of the square constituted by the single or built-up plates 25.

At the outer end of each of the electrodes 26 is located a two-part water-cooled metallic electric-circuit terminal 27. the two parts being bolted together by suitable bolts 28 which extend through laterally extending lugs or flange portions 29. Suitable cham bers 31 are provided in each of the two parts constituting the terminal 27, through which a cooling fluid may be circulated by means of pipes 32 suitably connected to the chambers 31 and a supply (not shown) of a suitable cooling fluid. Metallic terminal barsv 33 are located against the outer flat surfaces of each of the two parts of the terminal 27 by means of a plurality of bolts 34 to permit of conducting current to and from the electrodes and the heating element from a suitable source of supply of electric energy (not shown). A plurality of suitable openings is provided in the side walls of the casing 12 to permit of bringing out therethrough the bars 33 and the pipes 32.

In order to insulate the metallic terminal members 27 from the metallic casing and end plates, a suitable insulating member 35 'is placed between the outer end of the inof securing thereagainst a relativel short casing 39, the outer end portion 0 which engagesthe inner end of the terminal 27, slightly overlappin the same to provide a space between the p ate 14 and the inner end 7 of the terminal 27 within which a mass 41 of granular heatinsulating material, such as coke dust, may be placed. The mass 41 acts not only as a heat-insulating material but also as a'means for conducting current from the inner surface'of the terminals 27 to the outer intermediate surface of the electrodes 26. Substantially the same construction as hereinbefore described for one end of the furnace illustrated in section in Fig. 2 is employed for the other end of the furnace, the details of which are indicated by the broken lines of Figs. 1 and 2. A baffle plate 42 of asbestos lumber is located at the inner end of each of the electrodes 26,

providing a space between each of'the plates 42 and 14 which is filled with a mass 43 of granular heat-insulating material, such as coke dust, which has been ground fine. Plates 44 of a suitable electrical insulating material. such as asbestos lumber constitute the lining of the furnace casing 12. Within the space immediately surrounding the heating element 24 is placed a mass 45 of finely divided granular heat-insulating material, such as coke dust. I Y

The furnace structure 11 comprises a horizontally extending bottom plate 46 of sheet metal which is spaced from the bottom part of the casing 12 by suitable angle bars '47. the plates 14 at each end of the furnace structure extending downwardly substantially as far as the bottom of the bars 47, thus providing a space between the bottom of the casing and of the furnace structure proper and also providing a relatively stiff bottom for the casing 12. A plurality of longitudinally extending rods 48 having threaded ends is employed to maintain the end Wall 21 in its proper operative location with reference to the casing 12 and, at the same time, to resiliently compress the heat ing element 24 and to press the electrodes 26 against the ends of the heating element. At one end of the casing 12, nuts 49 are placed upon the threaded ends of the rods 48, while, at the other end, a helical spring 51 surrounds the outer end portion of each of the rods 48, an adjusting nut 49 and washers 52 being provided on each of the rods 48 to permit of adjusting the compression of the plates and the electrodesagainst the heating element.

A plurality of laterally extending fiat bars 53 are located on the upper edge of the side portions of the casing 12, one of each being located above the ends of the heating element and one at the middle thereof, each bar being provided with an opening 54 therein to permit of placing th'erethrough a quartz observation tube 55 which may abut against the upper surface of the heating element 24 to permit of visual inspection of the heating element during the operation of the furnace.

As hereinbefore stated, both the heating element 24 and the electrodes 26 are provided with a plurality of spaced-apart chambers extending longitudinally therethrough for the passage of a plurality of refractory rods to permit of their being heat-treated thereby. Means for simultaneously pushing a plurality of rods through said spaced-apart chambers comprises a rodpushing means, designated generally by the numeral 56. This means comprises a platform 57- of substantially the same width as the furnace structure and extending longitudinally at one end thereof, an angle member 58 being provided on the furnace structure to permit of securing the inner end of the plate 57 against the furnace itself. Supports 59 of metal are provided for the plate or table 57. cross members 61 being suit-ably secured thereto and a shelf 62 being mounted thereon to suitably support a driving motor 63 to operate the pushing means. The motor 63 is operatively connected, as by a belt 64, to a pulley 65 which is mounted on the outer end of a laterally extending shaft 66, on the other end of which there is mounted a worm 67 which is located in the casing 68. The worm 67 operatively engages a worm gear 69, also located in the casing 68, which worm gear is, in turn, mounted on a shaft 71 supported by suitable bearings in the casing 68. A gear wheel 72 is mounted on an integral extension of the shaft 71 on the outside of the casing 68 as to be forced to rotate therewith but to have movement longitudinally thereof. Av stop collar 73 is secured on the outer end of'the shaft 71 to limit the longitudinal movement of the gear wheel 72 in one direetion, the-casing 68 being effective to limit its movement in the other direction. The gear wheel 72 maybe moved longitudinally of the shaft 71 by an operating handle 74, in a manner well known in the art.

The gear wheel 72 meshes with a cooperating gear wheel 75 which is located on,'and has threaded engagement with, a threaded rod 76 which is supported in suitable bearing members 77. At the inner end of the rod 76 is located a. plate 78 which has secured thereto, at its inner surface, a plurality of rods 79, equal in number and substantially similar in spacing, to the number and the spacing of the openings through the electrodes 26 and the heating element 24. A pluralityof longitudinally extending troughs 81 are secured, at one end, to the end structure of the furnace 11, as against members 82, and, at the other end, against a plate 83 having a plurality of spaced openings 'the-rethrough, through which the rod 79 may extend. A plurality of bolts 84, suitably mounted on the plate or-table 57 and extending through suitable openings in the plate 78, prevent any turning movement of the plate 7 8 andof the rod 76 when the gear wheel 75 is given a turning movement thereon by means of the gear wheel 72. hen the motor 63 drives the pulley 65, the gear wheel 72 is caused to rotate and causes the gear wheel 75 to have a turning movement on the threaded rod 7 6 which causes the rod to move in a predetermined direction longitudinally of the furnace so that rods to be heat-treated in the furnace which have been placed in the troughs 81 may be pushed forwardly in a direction to cause them to enter the electrodes or to cause them to move a. plurality of rods which have already been moved partly through the chambers in the furnace still further forward and to cause other rods located at the end to move outwardly onto substantially similar trough members 81 at the other end of the furnace, from which they may be removed by the operator. The other end of the troughs 81 at the delivery end of the furnace may be supported in any suitable or desired manner, where indicated, as by supporting members 85.

When the rod-pushing means has been moved to substantially the end of its travel so that the outer ends of the rod 79 are close to the receiving end of the furnace structure, the rod 76 and the push rods 79 may be broughtback to their initial starting position by a quick-return motion comprising a shaft 86 mounted in suitable bearing members 87 and carrying, at its outer end, a hand wheel 88, and a gear wheel 89 located intermediate of its ends and in such position as to mesh with the gear wheel 75. When it is desired to move the rods 79 back to their starting position, the operating handle 74 is so moved as to cause the ear wheel 72 to become disengaged from t e gear wheel 75, after which the hand wheel 88 may be operated manually to cause the rod 76 to move in the opposite direction to bring the push rods 79 back into such po sition that another set of rods to be heat treated in the furnace may be placed in the troughs 81. The operating handle 74 may then be so moved as to cause the gear wheel 7 2 to mesh with the gear wheel when the operation of slowly pushing a plurality. of rods through the furnace will-be repeated.

The furnace embodying my invention thus provides a furnace comprising a plurality of chambers extending through a heating element and electrodes operatively engaging the heating element, said heating element and said electrodes comprising solid refractory material, such as carbon. As the resistance of a heating element of the above described. character is relatively low, the our- 7 rent required is relatively high in order to cause the-relatively high temperatures whlch are necessary to properly heat treat or anneal refractory resistance rods and I provide water-cooled metallic terminal members to conduct the current to and from the heating element and to maintain the terminals at a relatively low temperature.

My device provides a relatively small quantity of. granular heat-insulating material surrounding each of the electrodes immediately inside of the metallic. terminal member in order not only to assist in conducting current from the metallic terminal member to the electrode but also to assist in providing a gradually increasing temperature in the heating element, it being Well known, of course,"that the middle portion of an elongated heating element placed in a heat-insulating furnace structure will operate at the highest temperature and that the temperature decreases from the middle portion to the outer end portions thereof. This decrease may be non-uniform if no special provision is made and the relatively small mass 41 of'heat-insulating material greatly assists in causing this decrease to be uniform. The mass 4547f granular finely divided heat-insulating material not only reduces the amount of heat which is usually either radiated or conducted away from the heating element but also supports the heating elementwithin the furnace casing, therebymaking it unnecessary to depend entirely upon compression to maintain the individual units constituting the built-up heating element 24 in their proper operative positions within the furnace casing. The quickly movable doors permit of easily inspecting the condition of the granular heat insulating material surrounding the heating element during the operation of the furnace and also permit of tamping the granular materiahin place if this becomes necessary and also permit of quickly renewing any spent or damaged material. The granular material is parting from the spirit and scope thereof and I desire that only such limitations shall be placed thereon as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. In an electric-resistance furnace 101' heat-treating resistance rods, in combination, a heating element comprising'a plurality of flat refractory plates with their flat sides in abutting relation, each plate having a plurality of openings therethrough to constitute passageways through said heating element, and means for causing rods to be heattreated to move through said passageways.

2. In an electric furnace for heat-treating refractory rods, a heating element comprising a pluralit of thin flat refractory plates having their at sides located in abutting relation. each plate having a plurality of openings therethrough to constitute passageways through said heating element for the rods to be heat treated, and a granular material surrounding said heating element for supporting the same and for reducing the amount of heat radiated therefrom.

3. In an electric furnace for heat-treating refractory rods, a heating element comprising a plurality of thin fiat refractory plates having their flat sides located in abutting relation, each plate having a plurality of openings therethrough to constitute passageways through said heating element for the rods to be heat treated, and a comminutea granular non-electrical and non-heat conducting material surrounding said heating element and supporting the same.

4. In an electric furnace for heat-treating refractory rods, a heating element comprising a plurality of thin flat refractory plates having their flat sides located in abutting relation, each plate having a plurality of openings therethrough to constitute passageways through said heating.ele'

ment for the rods to be heat treated, a casing for said furnace, an insulating lining in said casing and finely divided granular non-electrical and non-heat conducting ma terial within said casing surrounding and supporting said heating element.

5. In an electric furnace for heat-treat-- ing refractory rods, a heating element comprlsing a plurality of thin flat-refractory plates having their fiat sides located in abutting relation, each plate having a plurahty of openings therethrough'to constitute passageways through said heating element for relation, each plate having a plurality of openings therethrough to constitute passageways through said heating element for the rods to be heat-treated, a casing for said furnace, finely divided heat-insulating material in said casing, surrounding and supporting said heating element and a plurality of spaced-apart electrical-insulating plates in said granular material.

7. In an electric furnace for heat-treating refractory rods, a heating element comprising a plurality of thin refractory plates having their flat sides located in abutting relation, each plate having a plurality of openings therethrough to constitute passageways through said heating element for the rods to be heat treated, an elongated refractory electrode at each end of said heat ing element operatively engaging the same and being provided with a plurality of open- .ings therethrough registering with the openings in said plates, and a water-cooled terminal member clampedon the outer end of each of said electrodes.

8. In an electric furnace for heat-treating refractory rods, a heating element comprising a plurality of thin refractory plates aving their flat sides located in abutting relation, each late having a plurality of openings theret ugh to constitute passageways through said ele'ment for the rods to be heat treated, elongated refractory electrodes operatively engaging the ends of the heating element and having a plurality of openings therethrough registering with the openings in said refractory plates, an open ended casing surrounding said heating element and said electrodes and having a portion operatively engaging the outer end of one of said electrodes, an end portion for said casing having movement relatively thereto longitudinally of said heating element and operatively engaging the outer end of said electrode, and means for resiliently pressing said end portion against said casing and for pressing said electrodes against said plates.

9. In an electric furnace for heat-treating,

' refractory rods, a heating element comprising a plurality of relatively thin flat refractory plates having their flat sides located in abutting relation, each plate having a plurality of openings therethrough to constitute passageways for the refractory rods to be heat-treated, an elongated refractory electrode at each end of said heating element operatively engaging the same, a. watercooled terminal member located at the outer end of each of said electrodes, :1 'quantity of granular heat-insulating material surrounding said heating element and the inner portions of each of said electrodes, a lesser quantity of granular heat-insulating material surrounding the intermediate port-ion of each of said electrodes whereby a uniform increase of temperature from the out- 1 er end of each electrode toward the inner end thereof is obtained.

10. In an electric-resistance furnace, for heat-treating refractory rods, in combination, a heating element comprising a plurality of relatively thin fiat refractory plates having their flat sides located in abutting relation to each other, an elongated refractory electrode at each end of said plates operatively engaging the same, said electrodes and said plates having a plurality of openings therethrough to constitute passageways for the rods to be heat-treated, means having a slow forward motion for pushing rods through said passageways, and means for quickly bringing said pushing means back to its starting position.

11. In an electric-resistance furnace for heat-treating refractory rods, in combination, a heating element comprising a plurality of relatively thin refractory plates having their flat sides located in abutting relation to each other, an elongated refractory electrode at each end of said plates operatively engaging the same, said electrodes and said plates having a plurality of openings theret-hrough to constitute passageways for the rods to be heat treated, and means for slowly pushing a plurality of rods in abutting end-to-end' relation through said passageways.

12. In an electric-resistance furnace for heat-treating refractory rods, in combination, a heating element comprising a plurality of relatively thin flat refractory plates having their flat sides located in abutting relation to each other, an elongated refractory electrode at each end of said plates operatively engaging the same, said electrodes and said plates having a plurality of openings theret-hrough to constitute passageways for the rods to be heat treated, and a mass of heat-insulating granular material surrounding all of said heating element and the inner portion of each of said electrodes in such quantity as to cause a uniform increase of temperature in said passageways from the outer end of said electrodes to substantially the middle of the length of the heating element when current is caused to traverse the electrodes and the heating ele ment.

13. In an electric-resistance furnace for heat-treating refractory rods, in combination. a heating element comprising a plurality of relatively thin fiat refractory plates having their flat sides located in abutting relation to each other, an elongated refractory electrode at each end of said plates opcratively engaging the same, said electrodes and said plates having a plurality of openings therethrough to constitute passageways for the rods to be heat treated, and means for pushing a plurality of rods in abutting end-to-end relation through said passageways, said means having a slow forward and a quick backward movement.

14. In an electric-resistance furnace for heat-treating refractory rods, in combination, a heating element comprising a plurality of relatively thin flat refractory plates having their flat sides located in abutting relation to each other, an elongated refractory electrode at each end of said plates operatively engaging the same, said electrodes and said plates having a plurality of" openings therethrough to constitute passageways for the rods to be heat treated, and electrically operated means for pushing a plurality of rods in abutting end-to-end relation through said passageways, said means having a slow forward and a quick backward movement.

In testimony whereof, I have hereunto subscribed my name this 21st day of March GEORGE M. LITTLE. 

